Multiple sequence block copolymers of silicones and styrene

ABSTRACT

Multiple sequence block copolymers of silicone and styrene having the formula: (1) (ABA)x ARE PRODUCED, WHERE A represents repeating diorganosiloxy units and B represents a polystyrene chain. This ABA chain is repeated from three to 10 times. The materials have high elongation and tensile strength and are useful in the formation of strong, elastic films.

United States Patent 11 1 Dean [ Sept. 18, 1973 MULTIPLE SEQUENCE BLOCKCOPOLYMERS OF SILICONES AND STYRENE [75] Inventor: John William Dean,Averill Park,

[73] Assignee: General Electric Company,

Waterford, NY.

[22] Filed: June 2, 1971 21 Appl. No.: 149,396

Related US Application Data [63] Continuation-impart of Ser. No. 26,082,April 6,

[52] US. Cl. 260/827, 260/33.4 SB, 260/33.6 SB, 260/93. 5 R, 260/93.5 A,260/874 [51] Int. Cl..... C08f 33/02, C08f 35/02, C08f 35/06 [58] Fieldof Search 260/827 [56] References Cited UNITED STATES PATENTS 3,678,1257/1972 Saam et a1. 260/827 3,678,126 7/1972 Saam et a1. 260/8273,051,684 8/1962 Morten et 31.... 260/827 3,187,031 6/1965 Weyenberg260/827 3,483,270 12/1969 Bostick 260/827 FORElGN PATENTS ORAPPLICATIONS 1,915,789 10/1969 Gennany 260/827 Primary Examiner-MurrayTillman Assistant Examiner-Wilbert J. Briggs, Sr. Attorney-Donald J.Voss and E. Philip Koltos [57] ABSTRACT 13 Claims, N0 Drawings MULTIPLESEQUENCE BLOCK COPOLYMERS OF SILICONES AND STYRENE This is acontinuation-in-part of parent application Ser. No. 26,082 filed on Apr.6, 1970 now abandoned.

BACKGROUND OF THE INVENTION Block copolymers of silicones and organicsegments have previously been described in the prior art. For example,block copolymers having silicone segments and polystyrene segments areshown in U.S. Pat. No. 3,187,031, issued June- 1, 1965. That patentteaches a variety of block copolymers of form AB, ABA and BAB, where Ais a chain of repeating diorganosiloxy units and B is a polystyrenechain.

The block copolymers of the prior art were produced, primarily, in orderto impart the properties of the silicone segments of the chain to anorganic material compatible with the organic portion. Polymers of theform AB, BAB and ABA, provide sufficient compatibility to allow blendingof the block copolymer with a compatible'organic resin as shown, forexample, in my copending application Ser. No. 26,083 filed of even datewith application Ser. No. 26,082. However, the single sequence blockcopolymers, i.e., one wherein, at most, one of the block segments isrepeated, do now allow full development of the strength properties ofthe materials.

SUMMARY OF THE INVENTION In accordance with the present invention,multiple sequence block copolymers of silicones and organic segments ofthe formula:

A): are prepared where A represents repeating diorganosiloxy units, Brepresents a polystyrene chain, and x is from three to 10. The preferredpolymers of this group are copolymers of polydiorganosiloxy blocks andpolystyrene blocks of the formula:

and a copolymer of the formula,

where R is selected from monovalent hydrocarbon radicals free ofaliphatic unsaturation, cyanoalkyl radicals and halogenated arylradicals, R is a radical selected from alkyl radicals, aryl radicals andaralkyl radicals, G is a divalent radical which is the residue from adian ionic polymerization initiator for styrene, such as the dialkalimetal reaction product of naphthalene, 1,1- diphenylethylene,l-phenylcyclo-hexene, anthracene, benzene, pentane and a varies from 10to 1,000, b varies from 24 to 1000 and x varies from 3 to 10, where a, band x are whole numbers.

A preferred method for forming the materials of formula (3) is throughreaction of a styrene monomer with an organic dilithium compound.Following this reaction, the form polystyrene has lithiated chainterminals. The lithiated polystyrene is then reacted with diorganosiloxymaterials, preferably hexaorganocyclotrisiloxane, to produce a singlesequence, ABA. This single sequence material also has lithiatedterminals and isof the formula:

The single sequence block copolymers of formula (4) may then be reactedwith a difunctional organosilicon material of the formula R SiY where Yis a functional group, the compound being reactive with the lithiatedterminal in such a manner that a removable lithium compound is formedwith the Y substituent, and the -SiR group is added to the chain. Thesingle sequence block copolymer of formula (4) may also be reacted withacetic anhydride to form the multiple sequence block copolymer offormula (2). i

If desired, the chain terminals of the single sequence block copolymerof formula (4) may be converted to silanol by reacting the singlesequence copolymer with lithiated chainterminals with an acid, such asacetic acid, to remove the lithium as lithium acetate, and form thesilanol terminals. The single sequence ABA block copolymer with silanolterminals can then be reacted with the material of formula R' SiY aspreviously de- DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordancewith the present invention, an nrgilttlt. monomer such as styrene isreacted with a dianionic alkali metal initiator for styrene so as toform an organic polymer having, for instance, lithiated chain terminalsof the formula:

The dianionic metal initiator compounds which may be employed in thisreaction include elemental lithium. Preferably, however, the lithium isemployed as an organic lithium compound including such materials asdilithium naphthalene, dilithium anthracene, 1,4- dilithium benzene,1,5-dilithium pentane, l,5-dilithium naphthalene, dilithiuml l-dipheny/ethylene, dilithium-l,phenyl cyclohexene, etc. Alkali metalssuch as the sodium and postassium forms of the above compounds may alsobe used as catalysts. The amounts of alkali metal catalyst or initiatornecessary is generally from about 0.000001 to 0.3 mole of the alkalimetal for each mole of the organic monomer, such as styrene.

The reaction of the organic monomer, such as styrene, with the dianoinicalkali metal initiator material is generally carried out in a solvent.Useful solvents include tetrahydrofuran, mixtures of tetrahydrofuran andtoluene containing at least 20% tetrahydrofuran, other ethers such asglyme and diglyme, and other aromatic hydrocarbons which are otherwiseinert to the reaction. The preferred solvent is tetrahydrofuran ormixtures of tetrahydrofuran and toluene. Purifications of productmaterials is more difficult when other ethers are used. This intialreaction generally requires several hours at C, at least when employingstyrene.

Following preparation of the dilithiated organic polymer of formulaterminal organosilicon blocks are formed by reacting the lithiatedorganic polymer with a polydiorganosiloxy material, preferably ahexaorganocyclotrisiloxane, such as hexamethylcyclotrisiloxane,hexaphenylcyclotrisiloxane, 1,3,5-trimethyll ,3,5-beta-cyanoethyl-cyclotrisiloxane, etc. to obtain the polymer of formula(4). Other cyclic, organosubstituted siloxanes can also be employed butreaction proceeds most easily with the hexaorganocyclotrisiloxanes.

The organosiloxane material which is employed in this reaction will, ofcourse, determine the R substituents on the polydiorganosiloxy blocks.Among the members which R can represent and, thus, the substituentspossible on the cyclic organosiloxane reactants are alkyl radicals suchas methyl, ethyl, propyl, isobutyl, hexyl, octyl, etc; aryl radicals,such as phenyl, naphthyl, biphenyl, etc; aralkyl radicals such asbenzyl, phenethyl, etc; alkaryl radicals such as tolyl, xylyl,ethylphenyl, etc; halogenated aryl radicals such as chlorophenyl,tetrachlorophenyl, chloronaphthyl, tetrafluorophenyl, etc; andcyanoalkyl radicals such as betacyanoethyl, gamma-cyanopropyl,gamma-cyanobutyl, etc.

The reaction of the dilithiated organic polymer and the diorganosiloxymaterial is carried out in the same solvent in which the organic monomerwas reacted with the dilithium catalyst. The reaction, particularlyemploying the hexaorganocyclotrisiloxane, generally requires from about2 to 4 hours at about 60 C.

The material which results from the reaction of the organosiloxanematerial with the dilithiated organic polymer is a single sequence, ABAblock copolymer, having a central organic polymer block and terminalpolydiorganosiloxy blocks which are, respectively, terminated withlithium as shown in formula (4).

Formation of the multiple sequence silicone-organic block copolymer canproceed directly employing this single sequence material, withoutpurification, or the single sequence material may be reacted with anacid, such as acetic acid, to produce a single sequence ABA blockcopolymer having silanol chain terminals. Similarly, the material withthe silanol chain terminals can be allowed to remain in the solvent andreacted to form the multiple sequence material, as explained below, orit may be purified and subsequently reacted with a polydiorganosiloxyunit of desired length having silicon hydride chain terminals accordingto reaction procedures which are well known for room temperaturevulcanizing organopolysiloxanes.

Employing an in situ reaction, either of the lithiated, single sequenceABA block copolymer or of the single sequence ABA block copolymers withsilanol chain terminals, a difunctional organosilane of formula R SiYcan be employed, where R is as previously defined, to form the polymerof formula (3). The substituents represented by Y are groups which arereactive with the alkali metal or which will remove the hydroxylterminal, without affecting the remainder of the block c0- polymer.Included among these groups are acyloxy groups, such as acetoxy, halogensubstituents such as chloro and aminoxy substituents. Specific materialswhich can be so employed include diphenyl diacetoxysilane,dimethyldiacetoxysilane, dimethyldichlorosilane, etc. This reactionproceeds relatively quickly under standard conditions.

With silanol chain terminals, the product can be removed from thereaction mixture and subsequently reacted with another material in orderto provide the multiple sequence block copolymer of silicone and organiccomponents. For example, the purified, silanol chain-terminated singlesequence block copolymer can be treated with a silanol condensationagent such as stannous octoate, or other organic metal salts whichcondense silanol units, either to directly couple to other singlesequence or short chain multiple sequence ABA block copolymers havingotherthan silanol chain terminals or with acyloxy or hydride-terminatedpolydiorganosiloxanes which may have chain lengths of up to 500, 1,000,or even more siloxy groups. In this manner, a room temperaturevulcanizing multiple sequence block copolymer can be formed andemployed.

Further, the dilithiated, single sequence block copolymer can be coupledto form the multiple sequence block copolymer of formula (2) throughtreatment with an acid anhydride, such as acetic anhydride, as explainedbefore. This reagent, added to the reaction mixture at 50 60 C acts toremove the lithium chain terminals and bond the siloxy groups from whichthe lithium has been removed If desired, following formation of themultiple sequence block copolymer, the silanol chain terminals can beconverted to other polysiloxane chain terminals by means known in theart.

In order that those skilled in the art may be better enabled to practicethe process of the present invention, the following examples are givenby way of illustration and not by way of limitation..All

parts in these examples are by weight. w

Example 1 cleaned equipment. Oxygen, water and other reactivecontaminants were excluded by purification of solvents and reactants.The solvents were purified by distillation, the toluene from sodium andthe tetrahydrofuran from sodium naphthalene. Thehexamethylcyclotrisiloxane reactant-was resublimated under reducedpressure, while the styrene reactant was redistilled under reducedpressure from calcium hydride.

A quantity of 260 parts toluene and 180 parts of tetrahydrofuran werecharged to the reaction vessel and 2.5 millimoles of dilithiumnaphthalene were added. The dilithium naphthalene was added as a 0.35molar solution in tetrahydrofuran. The mixture was cooled with anice-water mixture and 5.5 parts of styrene were added. AF ter 1 hour, anadditional 45 parts of styrene were added, in small portions, over thecourse of 1 hour. The solution became dark red and was kept at the low,ice temperature for an additional hour. A portion of a solution or 75parts hexamethylcyclotrisiloxane, in a mixture of 65 parts toluene and65 parts of tetrahydrofuran, was then added to the original reactionmixture. The mixture soon gelled, after which the ice water mixture wasremoved and the contents of the vessel heated to 60 C. The remainder ofthe hexamethylcyclotrisiloxane was added in small portions over thecourse of 3 hours to the slowly stirred viscous mass which had becomecolorless. Stirring was continued for 2 hours after completion of theaddition of the h'examethylcyclotrisiloxane solution and 0.4 part aceticanhydride was added. The mixture was stirred for an additional hour andwas then allowed to cool overnight.

The resulting product was diluted with additional toluene and was thenprecipitated into 4 volumes of methanol. The resulting product was arubbery, white crumb and was obtained in a yield of 88 parts. Theintrinsic viscosity of the material, measured in toluene at 25 C, was0.48 dl/g. This material had a formula equivalent .to formula (2), wherea is 200, b is 200, and x is greater than 2.

The polymer obtained was dissolved in various solvents and films werecast from these solvents. After evaporation of the solvent, 2 inchdumbbells were-cut from the films in order to measure the strengthproperties'of the material. The properties of these films, as determinedby the dumbbell measurements, are as follows, indicating the solventemployed for casting of each:

TABLE I Tensile Elongation Casting Solvent Strength (psi) n-hexane 512375 methylethyl 1,015 500 ketone-90% n-hexane 13% methylene chloride-951 500 87% n-hexane Example 2 A single sequencestyrene-organopolysiloxane block copolymer was formed in the same manneras in Example 1, through the reaction of styrene with dilithiumnaphthalene, followed by reaction with hexamethylcyclotrisiloxane. Theamounts employed were such as to form a material equivalent to formula(2) where a was 100, b was 50, and x was 1, and the block copolymer wasterminated 'with hydroxy groups. After recovery of the silanolterminated single sequence block copolymer, a quantity of 100 parts ofthe copolymer was reacted with 1 part of a 2 molar solution of [(CHCHNH] SI(CH in toluene. The copolymer had been previously dissolved inparts of toluene and was stirred while the amine was slowly added to it.The mixture was refluxed for a period of 2 hours and reaction was thenstopped by addition of acetic acid. The polymer was filtered from thesolution and the remaining solvent was then stripped. The resultingproduct was a rubbery, yellow mass which could be cast to a film from atoluene solution.

Example 3 Into a reaction vessel were placed 170 parts of toluene and 45parts of tetrahydrofuran. To this solvent mixture was added 2.5millimoles of dilithium naphthalene in the form of a tetrahydrofuransolution. A small amount of styrene was added to seed the catalyst and,after 15 minutes, an additional 25 parts of styrene were added over thecourse of an hour. The solution was initially dark red but became aclear red by the end of the styrene solution addition. A solution of 74parts of hexamethylcyclotrisiloxane in amixture of 65 partstetrahydrofuran and 65 parts of toluene was then added tothe polystyrenesolution with gelation of the solution occurring after about 1/5 of thehexamethylcyclotrisiloxane solution had been added. Addition of thehexamethylcyclotrisiloxane solution was continued over the course of l kto 2 hours while the reaction mixture temperature was raised to 50 60 C.A quantity of 0.3 part of acetic anhydride was added, incrementally,over a period of 10 minutes. The solution was diluted with methylenechloride and precipitated into 2,400 parts of methanol. The white,rubbery crumb was dried at 60 C in hot air and provided an 84 percentyield, based'on the theoretical. The material could be cast into a filmwhich was elastic and stronger than the corresponding film formed fromthe single sequence ABA block copolymer. The-structure of this materialwas equivalent to formula (2) where a is 200, b is 100 and x is greaterthan 2. In intrinsic viscosity of the material was 0.48.

EXAMPLE 3 In the same manner as in Example 1, a multiple sequencecopolymer was prepared having the structure of formula (2), where a is400, b is 100 and x is greater than 2. A solution of this material wasformed in a mixture of 87% n-hexane and 13% methylene chloride. Thematerial could be drawn with an extension of about 110 percent. Onrelaxing, the extension was approvimately to percent. On heating at 74C, the material shrank further to about a 55 percent extension.

EXAMPLE 4 Proceeding in the same manner as in Example 2, a blockcopolymer was formed having a structure equivalent to that of formula(2) where a was 400, b was 200 and x was 2. The intrinsicviscosity ofthis material was 0.73 and a rubbery sheet could be cast from a solutionof hexane containing 9 percent methylene chloride.

EXAMPLE In the same manner as in Example 2, a multiple sequence blockcopolymer was formed corresponding to formula (2) where a was 200, b was200 and x was approximately 3. The material had an intrinsic viscosityof 0.75 dl/g measured in toluene at 25 C. The increased chain length wasaccomplished through slower addition of the acetic anhydride in thecoupling reaction.

Films were cast from a hexane solution of this material, the hexanecontaining l0% ethyl acetate. The tensile strength of the film was l,200psi and the elongation 235 percent. The film could be cold drawn.Similar films cast from toluene showed a tensile strength of 970 psi andan elongation of 210 percent, while films cast from hexane with percentmethylethyl ketone had a tensile strength of 1,250 psi with anelongation of 290 percent.

EXAMPLE 6 Employing the same techniques as in Example 2 and using thephenyl diacetoxysilane coupling agent, a multiple sequence blockcopolymer having a composition equivalent to formula (2) was formed. Inthe copolymer relative to formula (2), a was 25, b was 50 and x wasapproximately 10. The intrinsic viscosity of the material was 0.19 dl/gin toluene and 0.16 dl/g in methylethyl ketone.

As the solvent cast films formed from the materials of the presentinvention are not chemically crosslinked, their strength must beotherwise derived, and it is believed, without wishing to be bound bytheory, that this strength is obtained through physical crosslinking.The physical cross-linking is believed to be obtained throughaggregation of the glassy, organic polymer blocks of adjacent chainsinto domains, thus establishing a network of tie points between thepolymer chains, with the connecting links between these domains beingthe polysiloxane chain segment. The range of properties of the blockcopolymers according to the present invention can be varied from stiffand inelastic to soft and rubbery, depending upon the relative organicand polysiloxane contents.

I claim:

1. A multiple sequence, block copolymer of polystyrene andpolydiorganosiloxane of the formula,

Ii. L J. L J.-.

where G is the residue of a dianionic initiator for styrene, which aredialkali metal reaction products of compounds selected from the classconsisting of naphthalene, diphenylethylene, l-phenylcyclohexene,anthracene, benzene and pentane, R is selected from the class consistingof monovalent hydrocarbon radicals free of aliphatic unsaturation, arylradicals and cyanoalkyl radicals, a varies from 10 to 1,000, b variesfrom 24 to 1,000 and x varies from three to 10, where a, b and x arewhole numbers.

2. The multiple sequence, block copolymer of claim 1 wherein a is from25 to 500, b is from 50 to 500 and x is from three to 10.

3. The multiple sequence, block copolymer of claim 1 wherein R ismethyl.

4. The multiple sequence, block copolymer of claim 1 wherein R isphenyl.

5. A film formed from the multiple sequence, block copolymer of claim 2.

6. A multiple sequence, block copolymer of polystyrene andpolydiorganosiloxane of the formula,

where G is the residue of a dianionic initiator for styrene, which aredialkali metal reaction products of compounds selected from the classconsisting of naphthalene, diphenylethylene, l-phenylcyclohexene,anthracene, benzene and pentane, R is selected from the class consistingof monovalent hydrocarbon radicals free of aliphatic unsaturation, arylradicals and cyanoalkyl radicals, R is a radical selected from alkylradicals, aryl radicals and aralkyl radicals, a varies from 10 to 1,000,b varies from 24 to 1,000 and x varies from three to 10, where a, b andx are whole numbers.

7. The multiple sequence, block copolymer of claim 6 wherein a is from25 to 500. b is from 50 to 500 and x is from three to 10.

8. The multiple sequence, block copolymer of claim 6 wherein R is methyland R is phenyl.

9. A film formed from the multiple sequence, block copolymer of claim 6.

10. A process for forming a polymer of the formula,

.[lolilL L Li. I

O i cn-om o cm-cn io i L ii. i Ll J.-. .2

comprising reacting a compound of the formula,

It u

with acetic anhydride, where G is the residue of a dianionic lithiuminitiator for styrene, which is a reaction product of lithium andcompounds selected from the class consisting of naphthalene,diphenylethylene, lphenylcyclohexene, anthracene, benzene and pentane, Ris selected from the class consisting of monovalent hydrocarbon radicalsfree of aliphatic unsaturation, aryl radicals and cyanoalkyl radicals, avaries from 10 to 1,000, b varies from 24 to 1,000 and x varies fromthree to 10, where a, b and x are whole numbers.

11. The process of claim 10 wherein R is methyl.

12. A process for forming a polymer of the formula,

with a compound of the formula,

R SiX where G is the residue of a dianionic lithium initiator forstyrene, which is a dilithium reaction product of lithium and compoundsselected from the class consisting of naphthalene, diphenylethylene, 1-phenylcyclohexene, anthracene, benzene and pentane, R is selected fromthe class consisting of monovalent hydrocarbon radicals free ofaliphatic unsaturation, aryl radicals and cyanoalkyl radicals, R is aradical selected from alkyl radicals, aryl radicals and aralkylradicals, X is selected from acyloxy radicals, alkoxy radicals, aminoxyradicals and halogen radicals, a varies from 10 to 1,000, b varies from24 to 1,000 and X varies from three to l0, where a, b and X are wholenumbers.

13. The process of claim 12 wherein R is methyl and R is phenyl.

2. The multiple sequence, block copolymer of claim 1 wherein a is from25 to 500, b is from 50 to 500 and x is from three to
 10. 3. Themultiple sequence, block copolymer of claim 1 wherein R is methyl. 4.The multiple sequence, block copolymer of claim 1 wherein R is phenyl.5. A film formed from the multiple sequence, block copolymer of claim 2.6. A multiple sequence, block copolymer of polystyrene andpolydiorganosiloxane of the formula,
 7. The multiple sequence, blockcopolymer of claim 6 wherein a is from 25 to 500, b is from 50 to 500and x is from three to
 10. 8. The multiple sequence, block copolymer ofclaim 6 wherein R is methyl and R'' is phenyl.
 9. A film formed from themultiple sequence, block copolymer of claim
 6. 10. A process for forminga polymer of the formula,
 11. The process of claim 10 wherein R ismethyl.
 12. A process for forming a polymer of the formula,
 13. Theprocess of claim 12 wherein R is methyl and R'' is phenyl.